Fuel injection pump for internal combustion engines



Fb. 24,1970 BSSIR'E 3,496,876?

FUEL INJEoTiQNIMP'FR INTERNAL comusiou ENGINES,

` mea Nov. 17.1967 SShetS-She 1 TMs/L0? I 'l Feb. 24, 1970 .P. E.BESSIERE 3496,76

FUEL INJECTION PUMP FOR INTERNAL COMBUSTION ENGINES Filed Nov. 17, 19675 Sheets-Sheet 2 Pierre E. essvrze Feh 24, 1970 P. E. BESSIERE 3,496,876

FUEL INJECTION PUMP FOR INTERNAL coMBUsTIoN ENGINES Filed Nov. 17, 1967v .'5 Sheets-Sheet 5 Phew@ E. Bess- Re- United States Patent O 3,496,876FUEL INJECTION PUMP FOR INTERNAL COMBUSTION ENGINES Pierre E. Bessire,Paris, France, assignor to Robert Bosch G.m.b.H., Stuttgart, Germany, acorporation of Germany Filed Nov. 17, 1967, Ser. No. 683,977

Int. Ci. F04b 49/00, 19/02; F22b 7/00 U.S. Cl. 103-37 3 Claims ABSTRACTOF THE DISCLOSURE BACKGROUND OF THE INVENTION The invention relates to afuel injection pump for internal combustion engines, said pump being ofthe type including a rotary distributor having a head through whichthere extends a transversal bore receiving at least one -pump pistondriven by a stationary cam ring surrounding said head. The injectionpump further includes at least one control piston which, for the purposeof changing the timing of the injection, is exposed to a fuel pressurewhich, in turn, is responsive to the r.p.m. of the engine.

Fuel injection 'pumps of the aforenoted type are known wherein thecontrol piston displaces the cam ring for the purpose of changing theinstant when the fuel injection begins. Such a pump is described in U.S.Patent No.

2,660,992, entitled Automatic Timing Means for Fuel Pumps. Adisadvantage of an adjustable cam ring resides in the fact that the pumppistons act back upon the stationary cam ring and tend to angularlydisplace it by impact. Such an angular displacement of the cam ring ishighly undesirable since it would result in an accidental shift in thetiming of the injection. In order to counteract the forces tending toaccidentally displace the cam ring, a check valve has been installed inthe supply conduit for pressurizing the fuel that acts upon the controlpiston and further, a throttle-controlled discharge conduit has beenprovided for the relief of the pressure chamber over the control piston.

In another known fuel injection pump of the abovenoted type, the controlpiston includes a control valve responsive to the pressure of thecontrol fluid. Such a pump is described in U.S. Patent No. 3,116,728,entitled Liquid Fuel Pumps.

In addition to the accidental angular displacement of the cam ring, theafore-described pumps are disadvantageous in that they are relativelyexpensive, and due to the tangential arrangement of the control pistonexternally of, and with respect to, the cam ring, they take upsubstantial structural space.

It is still a further important disadvantage of the aforenoteddistributor-type injection pumps that the rotary distributor must have arelatively large control orice since, when the cam ring is angularlydisplaced, the position of said orifice also changes with respect to themouth of the pressure conduits.

Fuel injection pumps are further known wherein the pum-p drive shaftcarries cam means to drive the pump pistons radially arranged in thepump housing and wherein the timing of the fuel injection is varied bychanging the angular position of the distributor head with respect tothe pump drive shaft Iwhich is operatively connected 3,496,876 PatentedFeb. 24, 1970 ICC thereto. Such a pump is described in British PatentNo. 1,003,180 entitled Improvements in Fuel Injection Pumps.

SUMMARY AND ADVANTAGES OF THE INVENTION The principal object of theinvention is to provide an improved fuel injection pump of the ty-p'eincluding a rotary distributor head containing -radially operating pumppiston means driven by a stationary cam ring wherein the disadvantagesset forth hereinbefore are avoided.

Briefly stated, the invention resides in a novel cornbination of a fuelpump distributor containing radially operating pump piston means drivenby a stationary, angularly non-displaceable cam ring with control meansfor varying the angular position of the distributor head with respect tothe pump drive shaft to change the timing of the fuel injection. Thecontrol means comprises at least one control piston slidably disposed inthe distributor head parallel to the axis thereof. According to apreferred embodiment, the control piston, acted upon by anr.p.m.-dependent fuel pressure, displaces a coupling element threadedlyconnected to the drive shaft and to the distributor head. The couplingelement, by virtue of its threaded connection with the drive shaft andthe distributor head, will also cause, during its displacement, anangular shift between the shaft and the distributor head. The novelcombination eliminates the bulky features of both types of fuelinjection pumps (those according to U.S. Patent No. 2,660,992 on the onehand, and those described in British Patent No. 1,003,180, on the otherhand) and also obviates all other drawbacks referred to hereinbefore.

The invention will be better understood and further objects andadvantages will become more apparent from the ensuing detailedspecification of a preferred embodiment taken in conjunction with thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged axial sectionalView of a fuel injection pump according to the invention;

FIG. 2 is a view of one part of the pump taken along line II-II of FIG.1; and

FIG. 3 is a view taken along line III-III of FIG. 2.

DESCRIPTION OF A PREFERRED EMBODIMENT Turning now to FIG. 1, there isshown in its entirety a fuel injection pump comprising a rotarydistributor 2 including a distributor head 1 and an axle portion 2aintegral therewith. The distributor head 1 is provided with atransversal bore 3 in which there are slidably disposed, in spaced,axial alignment, two oppositely operating pump pistons 4. As best seenin FIG. 3, the pump pistons 4 are driven by a stationary cam ring 5 whenthe distributor 2 is rotated by a pump drive shaft 6 disposed in axialalignment therewith. The distributor head 1 is connected to the shaft 6by means of a coupling mechanism generally indicated at 7, thestructure, function and operation of which will be described in detailas the specication progresses.

The drive shaft 6, which journals in a pump housing 8, drives, *by meansof a key 9, a gear pump 10. The pressure delivered by gear pump 10Varies as a function of the r.p.m. of the engine. This pressure may beadjusted by means of a valve (not shown) disposed in a bore 11 of thehousing 8. The gear pump 10 communicates with a suction chamber 14 ofthe fuel injection pump through a pressure conduit 12 in housing 8 andan external conduit schematically shown at 13. The suction chamber 14 isformed by the internal wall poriton of the housing 8 and a large annualrgroove provided in a block 15 par- 3 tially extending into the housing 8and iixedly held with respect thereto.

Through block there extends an axial bore 16 which reveives the axleportion 2a of distributor 2. The distributor head 1 is disposedexternally of block 15 within pump housing 8. The pump pistons 4 workingin bore 3 of the distributor head 1 are in engagement through pushermembers 17 and rollers 18 with the inner cam face of the stationary camring 5 which is prevented from relative rotation with respect to housing8 by means of a locking pin 19 extending through the wall of the housing8 and protruding into the wall of the cam ring 5. From the pump workchamber 20 defined by the transversal bore 3 and the two adjacent endfaces of pump pistons 4, the fuel is delivered by known means, not shownhere, into pressure conduits and to injection nozzles associated withthe engine.

As best seen in FIG. 2, through the distributor head 1 there extends,spaced from bore 3, a further bore 21 which receives reciprocatingpistons 22. The bore 21 and the opposed end faces of the two pistons 22define a pump work chamber 23. The pump pistons 22, similar to the pumppistons 4, are in enagement with the inner face of cam ring 5 throughthe pusher members 17 and rollers 18. The common axis of the pumppistons 22 lies in a plane defined by the axes of the distributor 2 andthe injection pump pistons 4. The bore 21, pistons 22 and work chamber23 define an auxiliary pump which forms part of a system for varying thequantity of the injected fuel. This system, other elements (not shown)of which are disposed in block 1S, operates on the principle of fluidabutment Iand is described, e.g. in U.S. Patent No. 3,122,100, entitledSelf-Regulating Pumps in Particular for the Injection of Fuel IntoInternal Combustion Engines.

The coupling mechanism 7, effecting a change in the timing of theinjection, is actuated by control pistons 24 slidably disposed in bores25 which extend into the distributor head 1 parallel to the axisthereof. T he bores 25 are separated from one another by bores 3 and 21.The bores 25 extend approximately up to the plane which intersectslongitudinally the transversal bore 21 and is normal to the distributoraxis. The plane containing the axes of bores 25 and distributor 2 isnormal to the plane containing the axes of the pump pistons 4 anddistributor 2.

The suction chamber 14 communicates with bores 25 through a channel 26extending through the block 15, a circumferential annual groove 27-machined in the distributor axle 2a and channels 28 disposed withinsaid axle.

The coupling mechanism 7, for varying the timing of the injection,comprises a threaded I,bushing 29 having a multiple externalcoarse-pitch thread 30 which is in engagement with a complementa]internal thread 31 of a coupling member 32 keyed to drive shaft 6. Thebushing 29 is further provided with a multiple internal coarsepitchthread 33 which is in engagement with a complemental external thread 34of a stub shaft 35 integral with, or rigidly affixed to, the distributorhead 1. The threads 30, 31 on the one hand, and 33, 34 on the otherhand, are of opposed pitch.

For transmitting forces from the control pistons 24 to the threadedbushing 29, there is provided a plate 36 which is secured to the bushing29 by means of a snap ring 37. To plate 36 there are riveted stems 38each of which extends into a hollow control piston 24 and engages theinternal terminal face thereof through supports 39. A coil spring 40,compressed between the plate 36 and an annular shoulder of couplingmember 32, urges the threaded bushing 29 and plate 36 into their initialposition against the distributor head 1.

Between the drive shaft 6 and the stub shaft 35 there is compr$$1 ,aCoil spring 41 which urges stub shaft 35 and drive shaft 6 axially awayfrom one another. One radial end face of the coupling member 32 is inengagement with a cover plate 42 by means of a roller bearing 43, whileone radial end face of the distributor head 1 is in engagement with theblock 15 by means of a roller bearing 44.

As long as the engine operates at low rpm., the threaded bushing 29remains in engagement with the distributor head 1 by virtue of spring 40since the pressure in suction chamber 14 is relatively low andconsequently, the force of the fluid pressure exerted on control pistons24 does not yet effectively counteract the force of spring 40. If nowthe pressure increases in the suction chamber 14 due to the increasingoperational speed of the gear pump 10 caused by an increased r.p.m. ofthe engine, control pistons 24, plate 36 and threaded bushing 29 aredisplaced against the force of spring 40 in the direction of the driveshaft 6. An axial displacement of the threaded bushing 29 causesrelative rotation of the distributor 2 with respect to the drive shaft6. The result of the new angular position between the drive shaft 6 andthe distributor 2 is that the instant has been advanced when theinjection begins. The extent of the shift in timing is determined by theextent the pressure delivered by the gear pump increases in response tothe r.p.rn. of the engine.

The afore-described structure of the coupling mecha-v nism 7 isparticularly advantageous since, due to the very large pitch of thethreads for causing only slight angular displacements, the rotarydriving forces and the pushing forces of the pump pistons exert onlysmall axial pressures on the threaded bushing 29 and thus on the controlpistons 24.

What is claimed is:

1. In a fuel injection pump associated with an internal combustionengine, said pump being of the known type having (A) a rotarydistributor Pump (B) a pump drive shaft,

(C) a multi-part coupling mechanism operatively connecting said driveshaft with said distributor head, said mechanism adapted to transmit atorque from said shaft to said distributor head and, upon actuation,adapted to change the angular position of said distributor head withrespect to said drive shaft to thereby vary the timing of the fuelinjection, and

(D) pump piston means disposed in said distributor head andreciprocating radially with respect to the axis of said pump,

the improvement comprising:

(a) control piston means disposed in said distributor head and movablealong a path parallel to the axis of said distributor head and spacedfrom the path of reciprocation of said pump piston means,

(b) channel means in said distributor head communicating with saidcontrol piston means for admitting an engine r.p.m.dependent pressurethereto to cause displacement of said control piston means, and

(c) an axially movable member forming part of said coupling mechanismand drivingly connecting said shaft with said distributor head, saidmember being axially movable by said control piston means and, whenaxially displaced, effecting a change in said angular position.

2. A fuel injection pump as defined in claim 1, wherein said pump pistonmeans include two oppositely reciprocating pistons disposed in a singleradial bore in said distributor head, said control piston means includetwo control pistons disposed in said distributor head in two spacedbores parallel to the axis of said distributor head, the plane definedby the axes of said control pistons and said distributor is normal tothe plane defined by the axes of said pump pistons and said distributor.

3. A fuel injection pump as defined in claim 1, includhead axiallydisposed in said 5 6 ing an auxiliary pump having auxiliary piston means2,806,431 9/ 1957 Woyot 103-227 radially reciprocating in saiddistributor head, the axis 3,013,547 12/ 1961 Miracki et al. 123-139 ofsaid auxiliary piston means being contained in a plane 3,074,345 1/ 1963Scheow 103-173 dened by the axes of said pump piston means and saiddistributor head. 5 OTHER REFERENCES References Clfed 860,654 4/1959Great Britain. UNITED STATES PATENTS WILLIAM L. FREEH, Primary Examinar1,825,691 10/1931 Hall 103--38 X 2,227,631 1/1941 Carter. U'S' C1' X'R'

